Dev-PHP is a well-featured IDE for PHP. Fast and powerful, it is easy to use and has a lot of cool features : class browser, scripts preview, integration with PHP parsers, PHP-GTK library, and Xdebug of course. Dev-PHP-usb slips even into your pocket.

Edyuk is a free, open source, fast and lightweight development environment which supports C++ and Qt 4 out of the box and can be extended through plugins. It works under all platforms supported by Qt 4 (Linux, Mac, Windows, BSD, ...).

Monkey Studio is a cross platform IDE wich primary goal is to support all kind of Qt relating programming. This place is now a mirror, the new official downloads place is http://code.google.com/p/monkeystudio/

Visual Lua is the Integrated Development Environment (IDE) for Lua language. You may use it for debugging the scripts written using wxLua library where the event-handling takes place. It supports multithreaded debugging as well.